Process for the recycling of batteries, especially dry batteries

ABSTRACT

A process of recycling unsorted batteries. The unsorted batteries are led from a feeding bunker through a shredder directly into a rotary furnace as they arrive from the disposal collection. The shredded batteries are oxidatively burned at a temperature from 400° C. to 900° C. The resulting combustion gases are led via a gas cleansing installation consisting of a dust filter, wet washing filter and active charcoal filter. The oxidized product of combustion resulting from the combustion is fed to a metal winning process. The product of combustion may be burned once again in a further or later step by the rotary furnace after mixing with a reducing substance, coal, after which the resulting reductive product of combustion may again be fed to the metal winning process.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for the recycling of drybatteries or batteries containing cadmium, zinc, lead or alkali metalsusing pyrolitic methods, wherein the batteries may be unsorted and bepresent in shredded or unshredded form. The invention also relates toinstallations for performing the recycling process.

2. Description of the Prior Art

A large number of processes for recycling batteries are known in whichhowever the batteries must be sorted according to their composition andin which the individual process is suitable for one type of batteryonly. This is especially true for the known process of the S. N. A. M.company in Lyon, which is suitable only for the processing of Ni--Cdaccumulators. Further examples of processes for the recycling of sortedbatteries, e.g. used alkali-manganese and zinc-carbon batteries, havee.g. become known from the Japanese patents JP-A-74/106,519 andJP-A-75/60,414. Therein it is proposed to scrap the correspondingbatteries, to treat them with hydrochloric acid, and to separate outmanganese from the solution as hydroxide by neutralizing with NH₄ OH atpH 5, and as Mn₂ O₃ at pH 9 after addition of MnO₂ or H₂ O₂. Inaccordance with U.S. Pat. No. 3,438,878 zinc and manganese dioxide areto be won simultaneously in the electrolysis of a solution containingsulphuric acid. All these processes, which use sorted batteries as rawmaterial, are unable to succeed simply because the number of batteriesreturned is relatively small and always requires subsequent sorting.This means that the intake area for a given installation is so largethat the costs of collection are much too high. Various processes havebecome known which improve the sorting process, which processes follow aseparation according to chemical or geometric criteria. The rejectedquantity, however, still remains as a critical waste product.

An intermediate step is represented by certain processes which arerestricted to reducing the toxicity of waste containing mercury, inwhich the batteries are taken in unsorted. One example is the process ofthe Vost company in which the mechanically crushed batteries have theirmercury content removed in a vacuum at temperatures of about 400° C. Asimilar principle was put into operation in the Clean Japan Center byMitsui Metals Co. and Nomura Kosan Co. This method, which is known asthe CJC process, works in such a manner that the batteries are firstfreed from their metal cases and then thermally treated in two stages attemperatures of 600° C. -800° C.

The most recent processes are those in which unsorted batteries arerecycled. One solution is described e.g. by EP-A-150,821 of theMetallgesellschaft AG. Here, the small batteries are first mechanicallycrushed and certain additives added, whereupon this product is subjectedto a chloridizing roasting at a temperature from 580° C. to 700° C. Thevaporized mercury is washed out of the exhaust gas. The product ofroasting is then treated with dilute hydrochloric acid and the noblermetals then precipitated out of the solution by cementation with zinc.Sumitomo Heavy Industries Ltd. has developed a pyrometallurgical methodfor processing unsorted batteries. This process provides that thebattery scrap be put into a cupola furnace and then run through threesuccessive stages, namely an oxidation stage for distilling off themercury, a subsequent reduction stage for vaporizing the zinc, andfinally a high temperature melting zone in which the entire remainingresidue is processed to a fused product. Due to the direct succession ofthermal treatment zones in the cupola furnace, certain problems relatingto the development of dioxins and PCBs have been observed. Due to theunpredictability of the composition of the furnace charge, thetemperature control is extremely difficult to manage. A correspondingtest installation in Switzerland burned through. The problems were latereliminated.

Further, there is a process (CH-A 04 969/86-0) which in the mean timehas yielded positive results even in continuous operation. In thisprocess, the unsorted batteries are first subjected to a pyrolysis stagein which the organic constituents are burned and the water and mercuryare vaporized off. The product of pyrolysis is then shredded and washed,whereupon after addition of HBF₄ a solution results which can beseparated by means of electrolysis into various relatively very puremetal fractions. In an improved version (WO 93/20593) a second pyrolysisis now performed after the first pyrolysis and the subsequent shredding.

All known processes in which unsorted batteries are recycled have thegoal of separating the resulting mixture as far as possible intodifferent fractions which are as pure as possible. None of the knownprocesses with the exception of the last named process of the RecyctecSA company have ever reached the commercial phase. These processes canexist commercially only when the take-back price of the unsortedbatteries is high. This prerequisite is compelling since the costs ofthe installation are enormous.

SUMMARY OF THE INVENTION

The object of the invention is thus to create a process for recyclingunsorted batteries containing cadmium, zinc, lead or alkali metals,especially dry batteries, which require substantially lower investmentcosts for the installation, in order that the recycling costs may besubstantially reduced.

The invention is based on the consideration that the costs can bedecreased if the number of products provided for reutilization is keptlow. A separation of the output products into components was thus out ofthe question.

The expert immediately recognizes from the process in accordance withthe invention that this process can be realized with a few commerciallyavailable installation parts. The process essentially comprises simply afeeding bunker, a shredder, and a rotary furnace, as well as aconventional gas cleaner with cyclone or dust filter, wet wash filterand active charcoal filter. This process, which is substantiallysimplified from the point of view of the technical installation, isbased on the recognitions gained from the analysis of the oxidizedproduct of combustion. It turned out namely that this product ofcombustion is an exceptionally suitable raw material for thezinc/cadmium/lead reclamation in zinc works.

Depending on the situation with respect to purchase conditions and thecurrent raw material prices, the resultant product can be subjectedwithout further modification of the installation to a second combustionfollowing the oxidative combustion using the same means, wherein thecombustion proceeds reductively.

In a first step of the process, the elements which are especiallycritical toxically, are separated off and the remaining material isseparated in a second step into two, or a maximum of three, differentmaterial mixtures representing input products for known industrialmetallurgical processes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the process in the simplest, yetmost complete, variant;

FIG. 2 is a representation of the oxidative combustion process;

FIG. 3 is the second, reductive combustion process representing anoption and

FIG. 4 is a process with a first and a second treatment stage.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

The batteries as collected via the retail trade are of completelydiffering composition. Relatively strongly represented, for example, arealkali batteries, nickel/cadmium batteries, or lithium/manganese oxidebatteries, to name but a few. All these batteries arrive directly at afeeding bunker 1 totally unsorted and uncleansed, some in collectionpackages of cardboard or plastic. It is sensible, but not compulsory, towork with a feeding bunker, since it is advantageous to operate theprocess continuously over a longer period of time. There is also aquestion of economy. From the feeding bunker 1 the unsorted batteriesarrive at a shredder 2 via a feed line. The output of this shredderstands in direct connection with the subsequent furnace 3, so that theshredder 2 is suitable for the direct charging of the furnace. Theshredder is a part of the installation which can be obtained directly onthe market and used without modification. Merely the unconventionalconnection between the shredder and the furnace 3 requires specialmanufacture specific to the installation.

During the combustion taking place in the furnace 3, it is importantthat the material supplied during the combustion process be continuouslymixed since this enhances the combustion and improves the degassing. Inaddition, air must be continuously supplied. Such a combustion isadvantageously performed with a rotary furnace. This point will bereturned to hereinbelow in reference to FIG. 2. The combustion gases arelet out of the furnace and led to a gas cleaner 7. This gas cleaner 7 isalso an absolutely conventional industry standard. The gas cleaner 7here consists of a first cyclone or dust filter 4, by means of whichdust present in the corresponding exhaust gases is separated off,whereupon the remaining gases arrive at a wet washing filter 5. In thewet washing filter 5, the mercury vapors, in particular, are condensedout. Some remaining ppm of mercury may succeed in passing through thisfilter and are thus, again in a known manner, removed from the exhaustgases by means of an active charcoal filter 6. The remaining gasescorrespond to the air cleanliness specifications and can be releaseddirectly into the atmosphere.

From the rotary furnace 3, an oxidized product of combustion P isobtained. This can be led directly or indirectly to the metal winningprocess 8. In the example represented here the conveyance of theoxidized product of combustion P proceeds directly to the metal winningprocess 8. Investigations have shown that the product of combustion P isexceptionally suitable as a raw material for metal winning. The productis free of mercury (residual amount less than 1 ppm), no longer containsorganic components; and consequently no dioxin or PCB residues resultfrom the subsequent processing in the metal winning process. Thecomposition of the product P results from the following list when theempirically determined percentages are taken into consideration.

    ______________________________________                                        Constituents     Percentage                                                   ______________________________________                                        ZnO              10-20                                                        CdO              2-4                                                          Fe.sub.2 O.sub.3 25-30                                                        PbO.sub.2        2-4                                                          MnO.sub.2        20-40                                                        graphite          5-10                                                        trace elements and                                                                             remainder                                                    salts                                                                         ______________________________________                                    

This product P, produced under laboratory conditions, was sent tovarious tin works and tested there for suitability as a raw product forthe zinc, cadmium and lead winning process. The investigation showedthat this raw material is suitable and contains substantially higherconcentrations of the metals to be won than the usual raw materials.

Especial emphasis was placed on the avoidance of dioxin and PCBcomponents. It is thus important that the following operating conditionsbe adhered to:

1. The charging of the furnace with freshly shredded batteries iscontinuous and in counterflow to the air intake.

2. The operating temperature in the rotary furnace is preferably 600° C.to 700° C. Under certain conditions temperature deviations downwardly toas low as 400° C. and upwardly to as high as 800° C. can be tolerated.The operating temperature can also increase in the direction of passage,is preferably held at first between 400° C. and 700° C. (first phase)and increased in further passage to and held at up to 900° C. (secondphase). Whereas in the first phase of combustion a decompositionavoiding dioxins and PCBs is achieved, the residual mercury iscompletely vaporized off in the second phase.

3. The duration of the combustion, i.e. the time spent by the batteryparticles in the rotary furnace, must amount to no less than half anhour to an hour and not more than ten hours. Advantageously it shouldamount to between 45 and 90 minutes.

These conditions are schematically represented in FIG. 2. With the sameinstallation, but without the shredder process, the oxidative product ofcombustion P can be further processed to a second, reductive product ofcombustion P'. This process is represented in FIG. 3. The rotary furnace3 is now charged with the oxidative product of combustion P along with aquantity of coal. The coal here represents a preferred reducing agent.Other reducing agents are however not excluded. In comparison with theoxidative combustion, the reductive combustion takes place at a highertemperature. This can, in principle, lie between 500° C. and 1300° C.,but should preferably be between 700° C. and 1100° C. The gaseouscomponents produced herein are initially distilled off. The remainingexhaust gases can be led through the exhaust gas cleansing processdescribed above. In this manner zinc, cadmium and, where present, leadare removed from the product of combustion P by distilling off thesemetals and reoxidation in the vapor phase. The reductive product ofcombustion P' remaining can in turn be sent to the metal winning process8. This product, which now consists principally of Fe₂ O₃ and MnO₂, hasbecome a raw material which steel works gladly accept asferro-manganese. The manufacture of this product of combustion P' willbe opted for in those cases where the product of combustion P is in lowdemand and consequently commands an especially low price. As aconsequence, the battery recycling works need not install a store forraw materials. The elements zinc, cadmium and lead distilled off in thesecond, reductive burning process can be sold anyway without difficulty.

The combustion in the second step takes place at a higher temperature,than in the first step. At this temperature the slag present in therotary furnace is reduced and metals are vaporized. By virtue of the airblown in, the metals oxidize again in the gaseous phase above the slag,form oxides in finest, solid form and are blown out of the rotaryfurnace with the remaining air into a multi-stage gas cleansing process.

Naturally, this simple process can also be augmented by means of certainoptions in order to split off special fractions, but this would in turnmake the extremely economical installation more expensive, and wouldpartially reduce the commercial advantages of the process. On the otherhand, such steps could be taken by the recipients of these products,especially when the required installations are already present at thesemetal winning works anyway.

In FIG. 4, the process is schematically represented. Beginning at asupply bunker 1 in which the batteries or the scrap produced from themare present, these enter directly or, as shown here, via a shredder 2and a feeding line 3' into a rotary furnace 4'. The rotary furnace ischarged from the one side and fired from the other side. The rotaryfurnace can be varied on the one hand with respect to the angle ofinclination and on the other hand with respect to the speed of rotation.Customary rotary furnaces have a length of 7-12 m. In the first stage,however, an overlong rotary furnace of 25-50 m can be employed, whichallows a substantial temperature drop from the input end to the firingat the output end. The degree of mixing can be adjusted via the speed ofrotation, whereas the angle of inclination varies the time of passage.In the case of batch operation, the rotary furnace can be suspendedhorizontally for a certain period of time and simply be inclined asneeded for discharging the solid product of combustion.

During the operation, the battery scrap passes through the rotaryfurnace from the charging end to the firing end. At the charging end, asealed off gas outlet 5' is provided, through which the non solidproducts of combustion arrive at a multi-stage gas cleansing process 6'.At the opposite firing end there is a burner nozzle 7', via which bothoil and air combined are blown into the rotary furnace 4'. At the firingend the rotary furnace 4' is provided with a sealed off dischargingdevice 8'. This first rotary furnace 4' is operated, at least in theregion of the input end, preferably up to the middle of the furnace,below that temperature which can lead to dioxin formation, namely below720 ° C. Temperatures between 500° C. and 700° C. are customary, and acombustion temperature of about 600° C. is especially preferred. Atthese temperatures it is ensured that the organic constituents burn awaycompletely and that water as well as any mercury that may be present isextensively vaporized. In the region of the output end of the firstrotary furnace, the temperature can be increased to 900° C. in order toensure a complete vaporization off of mercury to less than 1 ppm. Thisfirst treatment step leads to a weight reduction of 30% to 50% accordingto experience. As a consequence, 50 to 70% by weight of the quantitysupplied leave the rotary furnace 4' through the firing end. The 30 to50% by weight of volatile components leave the rotary furnace 4' via thesealed off gas outlet 5' and are cleansed in the multi-stage gascleansing process 6'. This is done in a first step by a cyclone or hotfilter 60, in which the fly components are filtered out, which can inturn be fed back into the process, e.g. via the shredder 2. Theremaining gases are passed through a wet cleaner 61 in which about 0 to1% by weight of mercury, if present, as well as 15 to 20% by weight ofwater are separated off. The thus cleansed gases are finally releasedthrough an active charcoal filter as cleansed exhaust gases.

The solid products of combustion of the first treatment step enter fromthe first rotary furnace 4' into a second rotary furnace 9. The secondrotary furnace 9 corresponds completely in construction to the firstrotary furnace 4'. At the charging side a sealed off gas outlet 10 and amulti-stage gas cleansing process 11 are again provided. At the firingside a sealed off discharging device 12 is correspondingly provided.Again a burner nozzle 13 protrudes through the sealed off dischargingdevice 12 into the rotary furnace 9. Here again the burner nozzle 13introduces oil as well as air into the combustion chamber of the rotaryfurnace 9. By means of a reducing agent supply 14, a reducing agent isintroduced into the second rotary furnace 9 at the charging end. Thiscan be done separately or together with the solid products ofcombustion, which are fed from the first rotary furnace 4' into thesecond rotary furnace 9. In the case of a joint supply the solidproducts of combustion from the first treatment step can be mixed priorto charging with the reducing agent before these are introduced jointly.Coal is especially suitable as a reducing agent. This is an especiallyeconomical reducing agent which simultaneously serves as an energycarrier. The solid product of combustion of the second treatment stepstill amounts to 20 to 40% by weight of the originally introduced weightof the battery scrap.

The combustion in the second treatment stage proceeds at a highertemperature than in the first treatment stage, namely at a temperature,from 900° C. to 1200° C. At this temperature the slag present in therotary furnace 9 is reduced and the zinc, cadmium and lead constituentsare vaporized. Due to air blown in via the nozzle 13, the zinc, cadmiumand lead constituents which are present in the gas phase above the slagoxidize and thus form the corresponding oxides in finest, solid form andare blown out of the rotary furnace 9 with the remaining air via thesealed off gas outlet 10 into the multi-stage gas cleansing process 11.Here as well, the volatile components blown out first arrive at a hotfilter 111, in which the now solid zinc, cadmium or lead oxides areseparated out. These form an oxide mixture which form a productdesignated as P1. This product represents approximately 30 to 50% byweight of the batteries or battery scrap initially input. The exhaustgases separated off in the hot filter 111 are again here in turn ledthrough a wet filter 112 before they are finally released into theatmosphere. The third cleansing step by means of an active charcoalfilter can be dispensed with here.

The slag discharged from the firing end of the second rotary furnace 9contains mostly iron, nickel and manganese metals as well as oxides anda residual component of impurities. This slag forms a secondreutilization product which is here designated as P2. This product P2 ishighly welcome as an input product for direct reutilization in the metalwinning industry. It may, however, be the case that a relativelyconsiderable component, namely about 3 to 6% by weight of the initialstarting product, consists of soluble salts. In this case, the slag isput through a washing and cooling unit 15. In this manner, the solublesalts can be separated out as a further product P3. This step of theprocess is especially worthwhile if a relevant portion of the solublesalts can be reutilized economically. This is especially the case forlithium salts. The remaining insoluble product is designated by P2' andhas essentially the same composition as the product P2 and is reduced inweight merely by the amount of the soluble components.

The exceedingly economical process in accordance with the inventionyields in principle merely two end products. The product P1, consistingof a mixture of zinc, cadmium or lead oxides, serves as starting productfor the common winning process of zinc and lead in the known cupolafurnace process of the Imperial Smelting Corporation. The cadmium oxidesalso contained in the product P1 can also be separated off withoutchanging the process. Consequently, the product P1 represents a saleableoutput product for the metal winning industry.

Whereas the product P1 represents the oxidation product of the secondtreatment step, the product P2 is the reduction product of the secondtreatment step. The product P2, the quantitatively largest constituentsof which are iron, nickel and manganese, can be sent directly to thesteel industry without further separation of this mixture. Theutilization of the product P2 in the steel industry corresponds toabsolutely conventional methods and need not be described further here.The same remark holds, of course, for the product P2' as well. Theproduct P3 only occurs if it is known that a substantial part of thesoluble salts contain valuable constituents which are reusable. Inprinciple the product P3 can always be dispensed with.

Preliminary calculations have shown that the process in accordance withthe invention reduces the recycling costs for unsorted old batteries bya factor of three to seven in comparison with the known procedures. Thereasons for this are many and varied. Firstly, the installation costsare extremely low in comparison with the known processes, secondly theprocess is completely nontoxic, and finally, the requirement ofexpensive energy is extremely modest. This results from two causes, thefirst of which is namely that in the first treatment step diverse metalsoxidize exothermally, and the second of which is that in the secondtreatment step the reducing agent is an economical energy carrier,namely coal.

The process in accordance with the invention can be operatedcontinuously as represented and described here by working with tworotary furnaces arranged in series, where the handling costs areextremely low, since the process can then run practically fullyautomated and almost without attendants, which represents a considerableadvantage in high wage countries. The process can, however, also beoperated with a single rotary furnace, in which case the operation iscarried out in batches. In this case, the second hot filter and thesecond wet cleanser can be dispensed with. This represents yet a furtherreduction in the already very low investment costs, which makes theprocess acceptable in developing countries as well, although the amountof work to be performed manually is increased.

In summary, the following may be noted: In order to reduce theinstallation costs for carrying out a process of recycling unsortedbatteries, a substantially simplified process is proposed. In it theunsorted batteries as they arrive from the disposal collection are ledfrom a feeding bunker (1) through a shredder (2) directly into a rotaryfurnace (3). In this process, the shredded batteries are oxidativelyburned at a temperature from 400° C. to 900° C. for a period ofpreferably 45 to 90 minutes. The resulting combustion gases are led overa gas cleansing installation (7) consisting of the known elements dustfilter (4), wet washing filter (5) and active charcoal filter (6). Theoxidized product of combustion (P) resulting from the combustion is fedto the metal winning process (8). The product of combustion (P) can beburned once again in a further or later step by the rotary furnace (3)after mixing with a reducing substance, coal, after which the resultingreductive product of combustion can again be fed to the metal winningprocess (8).

What is claimed is:
 1. A process for the recycling of batteries usingpyrolytic methods such that the batteries need not be sorted, the methodcomprising:placing the batteries into a shedder that continually chargesa furnace; performing an oxidative combustion in the furnace for atleast 30 minutes at a temperature in a range of between 400° C. and 900°C.; evaporating and separating off mercury; burning paper and plasticcomponents; producing an oxidized product of combustion during oxidationof metals; and feeding the oxidized product of combustion as a rawmaterial to a process for winning of metals.
 2. A process in accordancewith claim 1 wherein the batteries are dry.
 3. A process in accordancewith claim 1 wherein the batteries contain at least one of eithercadmium, zinc, lead or alkaline metals.
 4. A process in accordance withclaim 1 wherein the oxidized product of combustion is fed directly as araw material to the process for winning of metals.
 5. A process inaccordance with claim 1 wherein the oxidation of metals takes place at atemperature in a range of 600° C. and 700° C.
 6. A process in accordancewith claim 1 wherein the oxidation occurs at a temperature thatincreases in a direction of passage through the furnace.
 7. A process inaccordance with claim 1 wherein the combustion takes place duringcontinuous motion of the oxidized product of combustion and continuoussupply of a gas mixture containing oxygen.
 8. A process in accordancewith claim 1 wherein the combustion is performed in a rotary furnace. 9.A process in accordance with claim 3 wherein the oxidized product ofcombustion is fed to a zinc/cadmium winning process.
 10. A process inaccordance with claim 9 wherein the zinc/cadmium winning process is alsoa lead winning process.
 11. A process in accordance with claim 3 whereinthe oxidized product of combustion is fed to a lead winning process. 12.A process in accordance with claim 1 wherein the oxidized product ofcombustion is subjected to a second, reductive combustion with anaddition of coal at an increased temperature in a range of 500° C. to1300° C., and wherein gaseous components are removed and a remainingreductive product of combustion is fed to the metal winning process. 13.A process in accordance with claim 12 wherein the increased temperatureis in a range of 700° and 1100° C.